However, Mr Southey said an internal police inquiry later identified a crucial 11-minute delay in police officers being dispatched to the scene. They finally arrived 26 minutes after the 999 call for assistance was connected.

Mr Sarjantson, and his partner, Tracy Alexandra, who witnessed the attack and now cares for him, sued the Chief Constable of Humberside, claiming that the delay in responding to the call amounted to a breach of the European Convention on Human Rights.

Their damages claims were struck out by Judge Karen Walden-Smith last year, but now the couple are fighting on in an Appeal Court case which raises novel issues of great significance to every police force in the country.

Mr Southey argued that there had been a 'real and immediate threat' to Mr Sarjantson's life and that, under Article 2 of the Convention, the police were under a duty to do everything reasonable to promptly come to his aid.

"It is clear that anyone who got in the way of this violent group was at risk. Mr Sarjantson was plainly in need of urgent protection", he told the Master of the Rolls, Lord Dyson, Lord Justice McFarlane and Lady Justice Sharp.

However, Fiona Barton QC, for the Humberside force, said that a victory for Mr Sarjantson would place "a wholly disproportionate burden" on police forces nationwide.

Pointing out that it was almost five minutes into the call before the operator was given the address where the violence was unfolding, and almost seven minutes before Mr Sarjantson was named, she said there had simply been "no opportunity" to prevent the assault.

Whilst acknowledging the 11-minute delay in dispatching officers, the QC said there was no evidence that officers could possibly have been there in time to save Mr Sarjantson from the beating he received.

The force, she added, had met its Article 3 obligations to 'robustly and effectively' investigate the crime and prosecute the perpetrators.

Miss Barton told the judges: "This was a phone call to a fight. It is the type of call that the police receive very frequently. The police could not have known that there was an immediate threat to anyone. By the time of the call, the risk had already materialised; the fight was in progress."

Given the importance of the issues raised by the case, the Appeal Court reserved its judgment until a later date.